The entire disclosure of Japanese Patent Application No. Hei 9-326850 filed on Nov. 28, 1997 including specification, claims, drawings and summary is incorporated herein by reference in its entirety.
1. Field of the Invention
This invention relates to a conductive thin film, a capacitor using ferroelectric materials, high dielectric materials and a method of manufacturing thereof, more specifically the conductive thin film to be easily patterned by etching, the capacitor having electrode materials to be easily patterned by etching while easily forming layers with ferroelectric materials or high dielectric materials, and a method of manufacturing such capacitor.
2. Description of the Related Art
Ferroelectric materials such as PZT (Pb(Zr, Ti) O3) or SBT (SrBi2 Ta2O9) are used to manufacture capacitors that configure ferroelectric memories. Also, dielectric materials such as BST ((Ba, Sr) TiO3) and the like having a high dielectric constant in permanent dielectric substances are used to manufacture capacitors that configure dynamic random access memories (DRAMs). Annealing in an oxidation atmosphere at a range of 650 to 850xc2x0 C. is required to crystalize these dielectric materials after forming layers with the materials. Further, matching in lattice constant with that of adjacent materials composing electrodes is required in order to crystalize a layer(s) formed with the ferroelectric materials. In consideration of above-mentioned requirements, either of platinum (Pt), iridium (Ir) or an alloy of these metals having a stability in a high temperature as well as having similar lattice constant to the ferroelectric materials is used for configuring an electrode of the capacitors in above. Also, oxides of noble metals such as IrO2, RuO2, RhO2, RhO3, PtO2, OsO2 and the like are used for the electrode by itself or as part of a multi-layer composed with any of above-mentioned metals because of their conductivities.
As described above, not much oxidation disturbing crystallization and/or conductivity during the annealing for the crystallization is caused by using platinum (Pt), iridium (Ir) or an alloy of these for electrode as electrode materials, so that the any of these is suitable for the electrode of the capacitors in above. The electrode made of these materials, however, is formed by carrying out pattering with etching using a mask 23, after disposing a metal layer 22 so as to cover the surface of a substrate 21 as shown in FIG. 2(a). The noble metals Pt and/or iridium used for the electrode are well-stabilized in a chemical stand-point, so that no chemical etching can be carried out on these metals. In order to carrying out etching, a method called sputtering in which the metals(s) are physically removed such as with ion milling using an inactive gas (Ar or the like) by emitting ions need to be carried out. By carrying out such etching, molecular of the metal(s) to be etched, that of the metal(s) used for the electrodes themselves are flown out from the metal(s). The molecular adhere on surfaces to be etched of the metal layer 22 as well as both sides of the mask 23 as burrs 22a (side walls) as shown in FIG. 2(b). The burrs 22a thus adhere can not be removed by reaction because the burrs 22a are just composed of fine grains of platinum, iridium or the alloy of these metals. The side walls 22a remain as they are even when the mask 23 (photo resist layer) is completely removed as shown in FIG. 2(c). Consequently, this etching method can not be applied to the parts where requiring a fine work. The drawback is observed not only the noble metals themselves such as Pt, Ir, but also observed when oxides of the noble metals having conductivity such as one of IrO2, RuO2 is used.
Although, further improvements in etching so as to finish the electrode without forming side walls are required as a result of the recent trend in high-integration of semiconductor memory and the like, the conventional etching for making electrodes disturbs the improvements. Degradation of the characteristics of capacitors is arisen when the physical etching is carried out as a result of causing damage(s) on the surface to be etched of dielectric substances.
It is an object of the present invention to overcome the above mentioned drawbacks on the capacitors, and to provide a capacitor and a method of manufacturing the same having an electrode made of material(s) capable of carrying a fine work through etching while withstanding a high temperature thermal treatment for crystallizing dielectric materials such as ferroelectric materials and the like. It is another object of the present invention to provide a conductive thin film and a method of manufacturing a semiconductor device having the thin film made of material(s) capable of carrying a fine work through etching while withstanding a high temperature thermal treatment.
In accordance with characteristics of the present invention, there is provided a capacitor comprises a dielectric material composed by using at least one of a ferroelectric material and a high-dielectric material, and an electrode composed by using a material containing a noble metal, the electrode being formed on at least one side of the dielectric material, and wherein the material of the electrode contains rhenium (Re).
Here, the noble metal is defined as metals having stable characteristics in thermally and chemically, as well as having excellent electric conductivities, including gold (Au), platinum (Pt), iridium (Ir), osmium (Os), silver (Ag), palladium (Pd), rhodium (Rh) and ruthenium (Ru).
Moreover, the capacitor means not only a capacitor holding a ferroelectric layer between metal layers disposed therein, but also means semiconductors having an FET (field effect transistor) structure including a capacitor, in other words the semiconductor device having an MFS structure or similar structure in which both a ferroelectric layer and a gate electrode are formed in that order on a channel region located in a semiconductor substrate.
By constructing the capacitor in that structure, Re may be liberated at a relatively low temperature by combining with fluorine and/or chlorine and so on. Therefore, Pt and/or Ir existed adjacent to the liberated Re may also be liberated easily when Re existing in crystalline structures of Pt and/or Ir are liberated. In this way, reactive etching, not physical etching can be performed to noble metals.
The material containing a noble metal can be Pt and/or Ir, may also one oxide of a metal selected from a group of osmium (Os), iridium (Ir), platinum (Pt), ruthenium (Ru) and rhodium (Rh). Further, the electrode has a multi-layered structure made of a conductive material, and at least one of the layers forming the multi-layered structure contains the material containing a noble metal, and the one layer may contains rhenium (Re).
In accordance with characteristics of the present invention, there is provided a semiconductor device including a capacitor structure at least comprises a semiconductor layer, a dielectric material composed by using at least one of a ferroelectric material and a high-dielectric material located on the semiconductor layer, and an electrode formed on the dielectric material, wherein a material containing a noble metal adding rhenium (Re) is used for a material of the thin film.
Also, in accordance with characteristics of the present invention, there is provided a method of manufacturing a capacitor comprises the steps of forming an electrode composed by using a material containing a noble metal at least one side of a dielectric material composed by using at least one of a ferroelectric material and a high-dielectric material, and performing a patterning of the electrode by etching, wherein rhenium (Re) is added to the material of the thin film, and wherein the etching is in dry-etching by introducing either of fluorine gas or chlorine gas.
It is preferable to carry out etching with supplying the supply source for causing oxidation when dry-etching is carried out by introducing the chlorine gas. Because, Re can be liberated more easily as an oxygen chlorine. (ReClO3, ReCl4 O) as a result of sufficient supply of oxygen.
Further, in accordance with characteristics of the present invention, there is provided a thin film having a certain conductivity, the thin film being composed by using a material containing a noble metal, wherein the material contains Re.
In accordance with characteristics of the present invention, there is provided a semiconductor device comprises a semiconductor substrate, and a conductive thin film formed one of directly and indirectly on the substrate, wherein a material containing a noble metal adding rhenium (Re) is used for a material of the thin film.
Also, in accordance with characteristics of the present invention, there is provided a method of manufacturing a semiconductor device comprises the steps of forming a conductive thin film on a semiconductor substrate one of directly and indirectly, performing a patterning of the conductive thin film by etching, wherein a material of the thin film is made by using a material containing a noble metal adding rhenium (Re), and wherein the etching is in dry-etching by introducing fluorine gas.
Further, in accordance with characteristics of the present invention, there is provided a method of manufacturing a semiconductor device comprises the steps of forming a conductive thin film on a semiconductor substrate one of directly and indirectly, and performing a patterning of the conductive thin film by etching, wherein a material of the thin film is made by using a material containing a noble metal adding rhenium (Re), and wherein the etching is in dry-etching by introducing chlorine gas.
While the novel features of the invention are set forth in a general fashion, both as to organization and content, the invention will be better understood and appreciated, along with other objects and features thereof from the following detailed description taken in conjunction with the drawings.